基于各微结构因素作用规律的纳米晶固溶体薄膜强化机制

The knowledge limitation of strengthening mechanism is one of the main obstacles to the development of nanocrystalline alloys. What complicates the task is that microstructural factors have significant effects on each other and are difficult to decouple systematically as composition changes. This project plans to select nanocrystalline solid solution—the most basic structure of nanocrystalline alloys, use the method of two-demensionalnanocrystallinemultilayered films to isolate the effects of main microstructural factors including grain size, grain interior composition, grain boundary composition, and grain boundary width of nanocrystalline solid solution. In this way, the function, proportion, and variation trend of a specific single factor in nanocrystalline alloys can be revealed when only this factor changes. By comparing with three-demensionalnanocrystalline thin films, we can also figure out the roles and trend of microstructural factors respectively in nanocrystalline alloys. Furthermore, by improving the current strengthening formulae of microstructural factors based on research results, we can build a bridge to connect the mature strengthening theory to nanocrystalline alloys. In our project, films of the three main lattice types (FCC, BCC, and HCP) will be investigated to obtain the functional rules of microstructural factors, strengthening mechanism, and strengthening formulae for nanocrystalline solid-solution thin films. The investigation resultsnot only are suitable for films but also can provide reference for bulk nanocrystalline solid solution materials.

纳米晶合金中微结构因素随成分而改变的复杂性限制了对其强化机制的深入研究，强化机制的不完善是阻碍纳米晶合金发展的关键之一。本项目选择纳米晶合金中最基本的结构——纳米晶固溶体，采用二维结构纳米多层膜的方法，对纳米晶粒的尺寸、溶质含量、晶界的成分和宽度四个主要微结构因素加以“孤立”，通过单个因素的改变，揭示它们各自在纳米晶固溶体薄膜强化中的作用、相对权重和变化规律；结合与三维结构纳米晶薄膜的对比，厘清各因素在纳米晶固溶体薄膜强化中的作用和规律；进而基于实验研究结果对现有各微结构因素强化理论的计算公式加以修正，为这些成熟的强化理论适用于纳米晶固溶体薄膜搭建一个联通的“桥梁”。通过对面心立方、体心立方、密排六方三种主要晶格类型体系的研究，获得基于各微结构因素作用规律的，适用于纳米晶固溶体薄膜的强化机制和强度增量计算公式。这些研究结果不但可用于薄膜材料，也能对块体的纳米晶固溶体材料研究提供参考。

纳米晶合金的优异力学性能已被大量的实验研究结果所证实，成为获得高强韧材料的重要途径。然而，微结构因素随成分而改变的复杂性限制了对纳米晶合金强化机制的深入研究，强化机制的不完善是阻碍其发展的关键之一。针对这一关键问题，项目采用二维结构纳米多层膜的方法，从实验上实现了对纳米晶粒的尺寸和溶质含量以及晶界的成分和宽度四个主要的微结构因素的“孤立”，通过单个因素的独立改变，揭示了它们各自在纳米晶固溶体薄膜强化中的作用、相对权重和变化规律；并与三维结构纳米晶薄膜的强化效果进行对比和确认，厘清了各微结构因素在纳米晶固溶体薄膜强化中的作用和规律；进而基于实验研究结果对现有各微结构因素强化理论的强度增量计算公式加以修正，获得了基于各微结构因素作用规律的纳米晶合金薄膜强化机制和强度增量计算公式。. 这些研究成果在纳米晶固溶体薄膜主要微结构特征揭示和它们在薄膜强化中所起作用的揭示方面取得了新进展。. 项目完成期间，发表期刊论文10篇，其中SCI源9篇；培养硕士研究生4名。